Field of the Invention
The present invention relates to an image forming apparatus which reads an original, temporarily stores image data in a storage unit, and then transfers the image data to an image forming unit to form an image.
Description of the Related Art
There has been proposed an image reading apparatus which conveys an original onto an original platen glass to read images on a front side and a back side of the original at the same time (see U.S. Pat. No. 8,477,387). In this image reading apparatus, a sensor which reads a front side of an original and a sensor which reads a back side of an original are placed in proximity to each other, and it is possible to read an image on a front side and an image on a back side at the same time without inverting an original.
On the other hand, there has been proposed an image forming apparatus which temporarily stores image data, which has been read by an image reading apparatus, in, for example, an image memory, takes the image data from the image memory with predetermined timing, and transfers the image data to an image processing unit which in turn performs image processing (see Japanese Laid-Open Patent Publication (Kokai) No. 2000-280580).
According to the technique described in U.S. Pat. No. 8,477,387, in a one-sided mode and a double-sided mode, reading productivity is increased by changing image data transfer blank time periods (blank time periods between transfer of originals) according to whether an operating mode is the one-sided mode or the double-sided mode.
The technique described in U.S. Pat. No. 8,477,387, however, has room for improvement because no twists are added to a reading method or the like in the one-sided mode although reading productivity in the double-sided mode is increased.
Lately, it has become possible to reduce the time that elapses before output of a copy image on a first original from an image forming unit is completed after the first original is read (First Copy Output Time; hereafter referred to as “FCOT”) is reduced.
This is because when the time that elapses from depression of a copy start button by a user to reading of image data by an image reading unit and printing-out of the image data by an image forming unit is long, this makes the user wait for a long time, and as compared to a case where FCOT is short, total power consumption is high. In the following description, “reduce FCOT” is expressed as “improve FCOT”.